Homework... Well, is more like a project.. I am trying to build an Electromagnet which capable off pulling a certain amount of newton..
I done conversion from Newton to Tesla...
Now do i have define the tesla value..

There is an airgap between each leg, each leg has to pull a piece of metal with 3N, in the distance of 2 mm, i am quite unsure about the next one, but would the airgap between the the metal pieces have something to say?